A conventional bend conduit 3, as shown in FIG. 1, normally has a relatively large pressure loss when used with straight pipes 4, 5 and 6. The invention discussed forms a pipeline system, of which the fluid dynamic properties obey the following formula: EQU H=(p1-p2)/.gamma.=.lambda.(L/D)(Vm*Vm/2g)+.zeta.(Vm*Vm/2g),
Wherein
H stands for the (measured) total pressure loss
P1: the static pressure of the fluid at point 1 in FIG. 1
P2: the static pressure of the fluid at point 2 in FIG. 1
.lambda.: the friction factor of the straight pipe
Vm: the mean velocity calculated from orifice readings
.gamma.: the specific weight of the fluid
Lu: the distance between the upstream measured tap (point 1) and the entrance of the first bend conduit
Lm: the distance between the exit of the first bend conduit and the entrance of the second bend conduit
Ld: the distances between the exit of the second bend conduit and the downstream measured tap (point 2)
L: Lu+Lm+Ld
g: the acceleration of gravity
.zeta.: total pressure loss coefficient due to two bend conduits in FIG. 1
d: the diameter of the straight pipe
It is thus known that the total pressure loss (H) will be reduced if the total pressure loss coefficient(.zeta.) is smaller. In a pipeline system having two elbows, the value of pressure loss coefficient of the second elbow will be twice that of first elbow if the distance (Lm) is too short or two elbows are in a different plane (see FIG. 1). If a pumped fluid passes through the first elbow, as shown in FIG. 1, a strong spiral motion is produced before entering the second elbow, which results in an additional pressure loss. The pressure loss occurs because the fluid cannot travel enough length to eliminate the spiral motion and recover to its normal velocity distribution. An analysis of a fluid flowing through bend conduits will be made hereinafter by means of principles of fluid dynamics. Upon a fluid flowing through a conventional bend conduit, as shown in FIG. 2, the fluid passes from the straight pipe section to the inner 7 and outer 8 curved portion and to the adjacent straight pipe. The passage has a high pressure vortex zone 9 and low pressure eddy zones 10, 11 wherein the former will increase the resistance of friction along the fluid flow and the latter will induce a relatively large turbulent flow. This decreases the mean fluid velocity (Vm) and in turn increases the pipe cross sectional local velocity, or the pressure variations, thereby increasing the value of the pressure loss coefficient. The resistance of friction includes the inertial forces, caused by the centrifugal forces directed from the center of curvature acting at the vortex area 12, and the frictional shear force resulting from the boundary layer acting at the boundary area 13. In order to reduce the inertia forces caused by the centrifugal forces, it is proposed to decrease the acceleration of centrifugal force (V*V/R) (V stands for angular velocity) by increasing the radius of curvature (R) of the bend conduit. Prior arts are in the Bennett, U.S. Pat. No. 298,059. Bennett's bend conduit discloses forming an elbow conduit in such a way as to achieve an area of the inlet and outlet ends which join the main pipe to reduce the effects of friction and obstruction on the fluid thereby requiring less power to move the fluid. However, the Bennett patent is based on the area of the bend of intermediate section being twice the area of the first and second ends. Applicant's application is to increase the intermediate section by cutting off the corner of the inner portion and outwardly expanding the outer portion to a ball-like shape, and the area of the intermediate section is larger than the first end only. The second end may be either more or less than the area of the first end. The reason is very clear: wherein the intermediate section is enlarged by cutting off the edge of the inner corner and outwardly expanding the outer portion as a ball-like shape to provide the bend conduit with a low pressure loss coefficient whether the second end is large or small. Shaefer, U.S. Pat. No. 4,514,244, which is the same as Bennett, requires that opposite ends be of the same area size.